With the development of digital wireless communication technology, a wireless communication system having a composite transmission/reception relationship is necessary between multiple nodes. The largest problem to be solved in this system is to control interference between the multiple nodes.
In a cellular mobile communication system, interference between multiple nodes is largely divided into intra-cell interference and inter-cell interference. For example, the intra-cell interference occurs when one transmission cell transmits a signal to multiple users. Here, the transmission node knows all transmission signals, and positive cooperation is possible upon transmission. An example of the positive cooperation is dirty-paper coding in a multiuser environment. On the other hand, the inter-cell interference occurs, for example, when multiple transmission cells respectively transmit signals to their own users. Here, one transmission node knows only its own transmission signal, and positive cooperation between cells is impossible.
In third generation partnership project (3GPP), one of standardizations bodies for 4G mobile communication systems, a coordinated multi-point transmission (CoMP) technique has been introduced to control the inter-cell interference. An example of an intra-cell interference environment is multiuser multiple-input multiple-output (MIMO).
To use channel capacity in which the inter-cell interference exists, a transmission node should be informed of channel state information including all channel matrices. A recently introduced interference alignment technique [Reference Literature 1: Cadambe and Jafar, “Interference Alignment and Degrees of Freedom of the K-User Interference Channel,” IEEE Trans. Info. Theory] is known as a technique capable of maximally obtaining a spatial multiplexing gain or a degree of freedom. In this technique, the channel capacity may be obtained at a high signal-to-noise ratio (SNR). However, since the interference alignment technique is under the assumption that all reception nodes as well as transmission nodes should know channels between all nodes, implementation is difficult.
On the other hand, it has been confirmed that the channel capacity of a multiuser MIMO system, which is an environment where the intra-cell interference exists, may be obtained by the dirty-paper coding technique. However, a significantly complex coding technique such as a lattice code is required to implement dirty-paper coding, and also there is a difficulty that a transmission node should know channel state information (CSI) of all links.